DD-WRT isn't what it used to be anymore, the build environment is a mess, a lot of drivers are binary only and often you have to dig around in the forums to find which builds are stable. I had a lot of bad experiences with consumer grade wireless routers (Linksys WRT610N... $#!&) and building my own router was the best choice I ever made.
You can use OpenWRT on a broad range of devices and it has similar features as DD-WRT and also a very nice web-interface. It runs perfectly on low power embedded PC's such as PCEngines Alix (X86) or Ubiquity RouterStation (ARM). Nice enclosures and also complete pre-built systems can be found on eBay.
The best choice for wireless network cards would be Atheros based, using the ATH9K driver in Linux. Ubiquity (www.ubnt.com) makes some very decent high power versions (SR-71 series) and Wistron DNMA92 is perfect as a budget solution (can be found on the pcengines online store). The RouterStation Pro and some of the Alix boards allow you to connect multiple wireless network cards for Dual Band radios. I would strongly suggest to use 5 GHz in addition to 2.4 GHz for the devices that support it. The 2.4 GHz range is overcrowded.